This invention relates to a cooling arrangement for an internal combustion engine comprising an oil-cooled valve reciprocally mounted therein.
Diesel engines operating on high sulfur fuels, oftentimes containing vanadium compounds, periodically require "top end overhauls" or grinding of the exhaust valves and seats employed therein due to corrosion effects and exposure to high heat levels. Such corrosion tends to induce a "channeling" or "guttering" of the valve faces to accelerate such corrosion and to give rise to gas leakage past the valves and potential breakage of the valve heads. Corrosion also occurs on the top of the valve heads, tending to cause severe pitting which may also lead to valve head failures. A similar corrosion problem may be experienced at the valve seats should they become exposed to abnormally high temperatures and depending upon their metallurgical make-up.
Metallurgical solutions have not fully solved the corrosion problem due to the high temperature levels experienced by the valves during engine operation. Therefore, the state-of-the-art has made various attempts to cool the exhaust valves by packing them with metallic sodium or other suitable cooling medium, by circulating oil through the valves or by circulating water circumferentially about the valve seats. The former attempt has a tendency, for example, to raise the temperature level of the valve stems to thus reduce the service life of the tubular guides reciprocally mounting the valves in an engine.
Also, circulation of water about the valve seats or the circulation of oil through the valves for cooling purposes has not provided a final solution to the corrosion problem. Examples of such oil-cooled valves are disclosed in U.S. Pat. Nos. 3,911,875 and 3,945,356. Another problem encountered with valves of this type is a loss of structural integrity in the composite valve due to the various passages and tubes disposed therein for oil circulation purposes. A high structural integrity of the valve is required, particularly since it may vibrate during engine operation and may impact its seat with considerable force.